Communication system



0v. 5, 192., e. ROSENBAUM ET AL 1,734,231 COMMUNICATION SYSTEM Filed Nov. 25, 1925 2 Sheets-Sheet 1 my J. Y

Cl b C d 8 Time Imveniors BrunoRosenbozum and Otto Pohle.

Nov. 5, 1929. a osE A'uM ET-VAL COMMUNICATION SYSTEM Filed Nov; 23, 1925 2 Sheets-Sheet- 2 I I L.

Inventors .BrunoRos'enbaum and Otto P012 le per A ttbrney Patented Nov. 5, 1929 UNITED STATES PATENT, OFFICE ammo nosnmaaum AND or'ro ronLE, or BERLIN, GERMANY, AssreNoRs To rnn man on. ERICK 1-. Born G. 1m B. E, or BERLIN, GERMANY COMMUNICATION SYSTEM Application filed November 23, 1923, Serial No. 676,571, and in Germany septembcr 20, 1922.

Various methods have been employed hitherto for transmitting signals by means of electrical oscillations for usein telegraphy or telephony. For this purpose it has been 5 customary to install in the various stations transmitters for calling and transmitters for conveying telegraph signals or telephone messages. F or the same purpose receivers of the call signal and receivers of signal message 1 were also provided at these'stations. There have been also in existence combined transmitting and receiving apparatus'such that when switched in on a certain circuit, they were open to a call signal and by a change in switching re-arranged for message signalling. The same applied'to'the'receivers. In the latter case, however, it has been usual that the receiver whenswitched over to receive the calling signal, re uired less sensitivity than when connected or receiving telegraph or telephone messages.

This invention relates to a communicating system which is supplied with at least one call receiver in addition to a signal receiver, or

5 a combined. receiver in the way describedf' Considerfirst the condition of using a' 't of oscillations corresponding to"-one single wire between two or more stations, and consider further that such an oscillation issent along one single wire or one single assembly of wires 'oining these stations. This invention has orits, purpose such an arrangement that all'the stations connected to this single wire will know immediately that a call is being made, further, that an optical signal will appear showing that the line is busy and pre venting the operators of such stations from making any call themselves on the same wire (and on the same signal oscillation).'

Another object of this invention is that when a conversation on a train of oscillations is carried on between two stations, the other stations not engaged in the conversation are prevented from using the same wire. This is accomplished by having an optical signal appear which indicates that the line is busy, so that the same train of oscillations should not be used by the other stations for the transmission of signals or for disturbing calling signals. or for carrying on converernment calls). .It-may also be necessary to introduce emergency calls (as in wireless signallin between ships). For these emergency cases-t e invention provides a possibility for giving anemergency call signal, andfordistinguishing this, although still using the same oscillation.

In order to explain the above assumed case of connecting several stations with a single oscillation the following may be stated. It is immaterial whether an oscillation is radiated or directed along the wires, this signal oscillation will always be able tov maintain connection within its reach between two or more stations. If station A wishes to connect with a certain station B and for this purpose uses an oscillation of a certain frequency, this means that at the moment of the generation of the oscillations in, the transmitter of the station A, an equivalent of wires is bein laid,

or of connecting channels establishe between station A and all other stations whose calling receivers are tuned to the same oscillation and are within the reach of the signal. The equivalent operation is therefore as if wires were strung from station A to all stations tuned to the same frequency within the reach of this signal, and lasting as long as transmitter works on this frequency. As soon as a selected station 13 enters into connection with station A, the other stations within reach must not simultaneously use the same oscillation either for receiving or for transmitting. The invention thereforeprovides means which insure the exclusive use of this oscillation for connection between the two stations. This invention therefore provides, as it were, a wire between these two stations and prevents the use of the same Wire by other stations. If, however, the station A wishes to make the same connection to several stations, B, C, D, and so on, then the invention provides means to extend the same wire to all of these stations in the manner of a communication oscillation. Lastly, this invention provides a means to introduce into such normal connection an urgent or emergency signal on the same Wire, (meaning the same oscillation) at least for the purpose of calling.

The first method of this invention is that the frequency of the call and trafiic signal are identical. This still allows the use of selective reception and selective transmission at the receiving and transmitting stations respectively. The transmitting apparatus however is made so that the nature of the call signal may be changed in different manners. Thus, the call signals may vary in the length of time, for instance, each station may have a different length of time, one of them may have an uninterrupted signal of two seconds, the next an uninterrupted signal of three seconds and so on. Another form would have a call signal which may consist of two or more signal impulses of the same length oftime orof different lengths of time,thus giving it first an uninterrupted signal of one second, then an interval of one second, then another signal of one second, while for another station there may be three such signals. Furthermore, the length of time of the uninterrupted signals as above may be varied, or the number of signals, or the length of time of each signal among a number may be varied, or the length of intervals among the interrupted call signals may be varied. It is evident that by this means a large variety of different call signals may be arranged, always using the same call frequency.

This is referred to as a horizontal arrangement, that is, all the call signals are on the same frequency level. It is further possible to have a vertical arrangement, that is, with the signals at different frequency levels. For instance, the station B called on a frequency of 100,000 will switch over automatically after receiving this first signal, to another wave, say 90,000 frequency. The station C having received the same call signal of 100,- 000 will change over to a frequency of 110,000. The third station, D, may switch over automatically to a frequency of 80,000, and so on. The calling station will now give the second signal on a new frequency, of, say, 90,000, and thereby definitely call stat-ion 13. Thus, station B may have an arrangement for automatically ringing a bell when the second signal arrives. Simultaneously, an optical signal that this line is busy will appear on this and other stations. The bell will continue to ring until the operator will lift the receiver, or in other way respond to the call.

It is also possible to combine this horizontal arrangement with such vertical arrangement. This may be done as follows: A certain group of receiving stations would be tuned to the same signalling frequency. The calling station will give a signal on this frequency, either one uninterrupted signal or a combination signal as described above. This would permit a differentiation among further groups of stations, one, for instance, responsive to a call of one second in length, another group to a call of two seconds in length, and soon. \Vhether such a preliminary selection is made or not, it is possible to have a further selection by means of an arrangement which will automatically switch over the receiving sets to another frequency.

At the other stations, at which the second signal did not arrive, the receiver may automatically return to its original position, after having waited during a specially assigned interval, and not receiving the second signal. This waiting may be secured by mechanical means, the call receiver being retained in a certain position during a period of time by means of a clockwork operatinga release mechanism. This waiting terminates if the second signal does not arrive. It is evident now that at stations C, D, and so on, the call receiver-will automatically be switched over to its original receiving frequency, after having waited without any results for a second signal. As the messages between stations A and B go on at the original frequency of 100.000, the following will take place:

The call receivers at all other stations are continually affected by this frequency and will switch over after a certain period of time (say two seconds) to the second frequency, say 110,000, 90,000, and so on. Since this second frequency will not arrive, they will return again after the expiration of the waiting time to the frequency of 100,000, and the same operation begins again, as long as the conversation on 100,000 frequency continues. The call receivers may be constructed in such a way that as soon as the first signal of 100,000 frequency arrives, an optical signal busy will show up and will be maintained during the whole of the waiting time, and continue to be held on busy as long as the conversation goes on at another station. It may disappear only for a fraction of a second at the end of the waiting period, when the call receiver is returning again to its original frequency. 'This will give an instantaneous blinking of the optical signal busy and will under no circumstances permit the operator of stations C, D, etc., to operate his instrument and thereby disturb the conversation going on between stations A and B.

, It may be practical in cases of heavy service, using a number of stations, as for instance, for carrier wave transmission on high tension lines in industrial districts, with hundreds of stations connected, to combine a vertical arrangement with a horizontal arrangement. In such a case 'the first impulse "on this 90,000 frequency, picking out definitely the station called. If this, however,

would imply too much complication, it is pos-.

sible for a still smaller group of stations to change over to a. third frequencyof, say, 60,000 cycles. If, for instance, three stations are changed over to a frequency of 60,000, it is only necessary to supply selective signals of one, two or three seconds on this 60,000

frequency, picking out the station desired.

' The trafiic may be again carried on at 100,000

is to prevent the interfering station from cycles. In this case it is necessary to give all the other stations a sufliciently long waiting period, so that the return to the original position does not occur until'the call is completed. This would insure that the busy light signal will not disappear.

It is evident, however, that such anarrangement would allow only very few conversations, as a large number of stations are connected together with a single message frequency, for instance, 100,000. There are several ways of avoiding this difliculty. Thus,

several message frequencies vmay be used.

For instance, in the above vertical arrangement, supposing a call ends on a 60,000 fre quency, the messages may now be conveyed on the same frequency to station A, butthe call receiver of the other two stations, B and C, having the same frequency signal of 60,000, would return again to their original positions. If it happens that'one of these other stations, say station B, is again called on a frequency of 60,000, this call receiver will perform its duty, but when going on the 60,000 frequency, a busy signal will appear. The ringing bell, however, will not operategas the receiver of this station B would be arranged for a final signal of a certain length of time, and. since station 'A' blot out the final calling signal of station- B and not permit the bell. to ring on this station. The optical sign busy will continue to appear at this and other stations. Nothing listening in on this frequency of 60,000. If, on the other hand, the three stations'with the final calling signal of 60,000 frequency are assigned different message frequencies. such as 65,000, 61,000, and 58,000, then this listening would be impossible.

This invention is not limited to the messages carried on one frequency in both d1- rections, but may also be extended to mes-- sages between two stations on two different frequencies.

With the above horizontal arrangement, after the calling has been completed, all the call receivers may return to their original position, except that an optical signal busy will appear on those stations which have the same call frequency as the message frequency ofthe station in operation. This is signified by 'a blinking signal. Directions may be given to the operators to abstain from the use of apparatusundersuch-conditions, or else an automatic lock may be introduced, consisting of a relay which is operated by the call receiver in the same way as the optical signal busy and which would prevent the lifting of the receiver by the operator or operating any other switch on the receivers of the stations'not in operation.

Even more intricate arrangements may be provided to put out of action the device automatically when an urgent, or emergency, call arrives.

The emergency call may be introduced as follows: A call receiver mayhave a second position corresponding to the Waves otherwise not employed, for instance, by using two circuits of different frequencies, one corresponding in the previous instance to, say, a frequency of 100,000, and another to a frequency 015 130,000. This latter frequency will then serve for the emergency calls, which would be identical for all stations. Itv is possible to use the same receiving and amplifying valves by insertion of selective circuits emergency. The emergency call is thus transmitted at a frequency of 130,000. The conversation formerly conducted will be therefore interrupted and all of the stations must follow a rule and switchover to the emergency signal, which may be 130,000 frequency, as above, or any other requency.

A further arrangement for emergency signals. arises where the en'ier ency signals are not intendedto be conveyed stations, but only to a certain group. It is even easier in this case to give the emergency call properly. It is only necessary for all of the receivers of the stations in this group to return totheir original position of readiness for receiving as soon as a call has been completed. It is then only necessary to give a common combination of signals for this group, which may end, say, as at 60,000-frequency as above. When, however, this final frequency is reached, the receivers called may to all of the j switch in a second circuit or an additional coil tuned to a frequency of 130,000, never used under any other circumstances except for emergency. If the emergency call is assing at this time, it will operate the ca ling bell and switch out all the other messages. The operator of a station which may be r 2rrying on a conversation at this instant, would immediately inform his party that he is to receive an emergency call, and would then interrupt the conversation.

The same expedients can be used for transmission of telegraph or telephone signals, it is only necessary to provide a distinction between the length of time between telegraph signals and call signals.

It may be mentioned also that it is often possible to use medium or low frequencies for signalling, while high fre uency is used for messages. A further modi cation is possible by assigning to each group a definite initial call frequency, say five stations at 5,000 frequency, five stations at 10,000 frequenc etc.

In addition, it is possible that the ca 1 signal would indicate the type of transmission to be used, for instance, whether it is telegraphy, telephony, high or low frequency, multiple telephony or telegraphy, etc. An arrangement of phantom circuits may be called for which would reduce the number of channels required.

It will be evident to those skilled in the art that it will be necessary to make the conductors suitable to the purpose. For instance, for carrier wave operation, a group of lines may be used or a single line. Since the messages may be conveyed either at one frequency (horizontal arrangement) or with a number of frequencies (vertical arrangement), it is possible to pick out the system of lines which is most suitable for a certain frequency of transmission. For instance, it may be possible in transmitting on certain frequencies to tune a total len h of a line or a section of it by addition 0 coils, capacities, or both,

when such tuning means would act as choke coils for all other/frequencies. Interference may be prevented by properly protecting a group of wires by transposition. If, however,

several frequencies are used, as in the vertical ararngement, it is advisable to arrange the tuning over a wider frequency range, by giving the total group of wires a group tuning for each of these frequencies or by se lecting a single tuning with a flat resonance characteristic.

If a group of wires is used for transmitting single frequency or a group of frequencies, it is advisable to reduce the attenuation of this group or this signal wire by suitable tuning, and preventing interference by suitable counter-tuning.

In another modification, it is possible to arrange the receivers in cascade so that the .a manner that the first receiver called after completing the call puts to work a second one, and so on.

Having described the object of our invention, we will now give an illustration of the manner in which it is carried out.

Figure 1 is a diagrammatic representation of the calling arrangement on the transmitter.

Figure 2 illustrates the operation of this calling transmitter.

Figure 3 is a diagrammatic representation of the receiving circuit.

Referring to the drawings, we have shown in Figure 1 a panel of insulating material 1, of a circular form with shoulders 3 and 4. Shoulder 3 controls a contact lever 5, shoulder 4 a contact lever 6. The contact 5 when touching the opposite contact 7, inserts a relay 18, while the contact 6 switches in or out by means of the opposite contact 8, a coil or a section of a coil 25, or capacity, or both, belonging to the antenna tunin circuit, thus throwing the transmitter consi erably out of resonance with the signal frequency. In Figure 1 the transmitter is at rest, that is, switched off and the antenna circuit tuned, as contacts 5 and 7 are open and conta'c'tsfi and 8 closed and as thus coil 25 is short-.circuited. On the panel 1 there is a pin of insulating material 9 and a fixed contact'pin 10, the latter being connected through co l 25 to the contact 6. 0n the shaft 2 there is fastened a contact arm 11. In the rest position as shown, the contact arm 11 touches the stop 12, while on the other end it touches the pin 9.

.A clockwork not shown in the diagram tends to move the panel 1 in the direction of the arrow 14. A fairly weak spring which is not shown in the diagram tends to turn the contact lever 11 von the shaft 2 in the direction'of arrow 15. A dial, not shown in means of which the lever 11 ma be turned in the direction opposite the cloc ork, that is, in the direction of arrow 17, through an angle which may be predetermined in such anel 1 would return to the position shown, in a fixed length of time. This ad'usting knob attached to the dial is operate by hand, into a position corresponding to the call of a certain station, that is, to a certain frequency or a certain length of time. -When this adjusting knob is brought into this sition, it will simply cause contact 5 to touc contact 7 and operate the transmitter, which will then transmit continuously the frequency out of tune, since the contact arm 11 is touching pin 9 and the aim tacts 6 and 8 are open. When the working knob is released, the panel starts immediately returning to its original position, carrying with it pin 16 and thereby aflecting the movement 0 the remaining parts.

The panel 1 controlled b the clockwork will return at uniform spee in the direction the diagram,- provlded with stopping points and a working knob, carries 'a pin 16Lby of arrow 14'to its original position. Simultaneously the contact arm 11 which may have had the first position I, indicated b dotted line, is driven by the spring in the irection ofarrow 15 faster than the panel 1, and will assume a position II, touching contact 10 and Eventually pin 9 will again touch the contact arm 11, and will bring the anel 1 to "rest, at the same time switching o the transmitter and eliminating the out-of-tune wave of thet-ransmitter by making contact 6 touch contact 8f 26 represents. the antenna, 28 is a high'frequency generator coupled with the antenna circuit by means of an inductive coupling arrangement 27. 29 represents the ground connection ofthe antenna 26. Referring to Fig. 2, at point a of the horizontal axis which represents the time, the working knob has reached the position where the mechanism will later transmit a five second, 100,000 frequency signal. At point 6 this working knob is released and this 100,000

frequency signal is transmitted until point a is reached, after a lapse of five seconds. At this point contact arm ll has arrived at stop 12, and the transmitter will go on, but on a different frequency, that is, of 90,000. This frequency is transmitted until point (i, when panel 1 has returned to its rest osition and ,the transmitter is again switche ofl, and the call is finished. After this, the contact 18 is closed, for instance, by lifting off of the receiver at the calling station, indicated at point received, and immediately the 100,000 frequency is continually transmitted and used for telephonic or telegraphic communication.

It is of course possible instead of throwing the transmitter out of tune, to disconnect it entirely. Figure 3, which illustrates a receiving system, shows at terminals 20 and 24, connections with any suitable source of current; the terminal 24 may be the positive terminal and terminal 20 the negative terminal. Between terminals 22 and 23 there is a bell 30, while between terminals 24 and 25 there is a standard telephone instruYnent. This telephone instrument has a contact 31 which is opened as soon as the receiver is taken off the hook. The switches 32 are the usual type three-point switches, connected in one position to bell with the receiver and in the other position to the call receiver, while in the third position-it is switched off. The position connecting the call receiver may be also used for receiving eme'rgencysignals.

7 side of the current supply.

As soon as a call signal is received (for instance, 'a 100,000 frequency) a lever 33 of insulating material is moved by clockwork with a ma net 36 in the direction of arrow 34. This is ac ieved by having a galvanometer type relay responsive to the signal and lifting by its electro-magnetic action the latch holding the clockwork. At the same time an optical sign busy (35) will appear and the magnet 36 is excited-while the lever 33 is moved in the direction of arrow 34. It is evident that for this purpose the terminal 37 of the magnet must be connected to the minus The rotating lever 33 and the contact arm 38 are connected with terminal 37. A second contact arm 39 is arranged to rotate around the pin 40 and is held in position by the spring 44. If after a certain length of time contact 38 touches contact 39, the circuit is closed from terminal 37, via contacts 38 and 39, to the conductive pin 40,

coil 42, and hence to positive'terminal 24.

The coil 42 is thereby energized and causes contact 43 to turn against the force of s ring 44 in the direction, of the arrow as s own around the pin 45. This contact 43 will then arrlve on top of the double lever 47 which has in the meantime come down, rotating around pin 46, carried by arm 33.

Supposing -it is this station that is being called and that it requires a signal impulse of five seconds time. During such a time the process as described above will have taken place. The contacts 38 and 39 have touched and the bent part of 43 has turned over. The signal impulse has now ceased, the magnet 36 is switched off and the arm 33 tries to return by the action of a spring, which is not shown on the drawing, to its original position. Hence the bent part of 43, which is still touching the double lever 47 will tend to rotate it somewhat against the action of the spring 48, making this double lever 47 touch the arm 49. This closes a circuit from terminal 37 via contact 49, double lever 47, wire,46, coil 47 wire 48, terminal 25, and hence to the positive terminal of the current supply. This will close the automatic contact 50 and the terminal 37 is connected to the receiving current in spite of the fact that magnet 36 is disconnected. Also, the coil 47, has a second contact 51 which is closed, connecting terminal 22 and bell 30 in the circuit,

and causing the bell to ring. If, however,

the receiver is lifted, the switch 31 is opened, disconnecting coils 42 and 47 and switching off the bell. The bent part of 43 is then removed by spring 44 from the double lever 47 and the arm 33 returns to its original position.

If a signal of shorter period of time reaches the apparatus, it is evident that the magnet 36 becomes disconnected before the bent part 43 catches the double lever 47 and therefore the optical signal busy will disappear at once, as soon as the signal of, for instance, three seconds time, is over. The arm 38 may then return without inserting the bell in the circuit.

If however, the signal is of a longer period of time, for instance, eight seconds, then the apparatus moves beyond the position in which levers 38 and 39 touch. The1r ends will then slip dff one another and before the call signal ceases. Hence there will be no current between those two contacts. The bent part 43 which after five seconds period caught lever 47, is after five and one-half seconds again taken away by the spring 44, since contacts 38 and 39 are no longer touching and the coil 42 is de-energized. After eight seconds the lever 33 may again return without hindrance into its original position; In this latter case, in order to prevent the lever 33 from going too far down and causing the contacts 38 and 39 to hit heavily a ainst each other, the clockwork may be switc ed ofi' entirely after 5.7 seconds. This is done by means of contact 52 on arm 33, which hits lever 54 and thereby neutralizes coil 53 (contact 52, lever 54, and coil 53 are illustrated by a separated circuit in this diagram). Coil 53, when de-energized, stopsclockwork.

Having now particularly described and ascertained the nature of our said invention and in what manner the same is to be performed we declare that what we claim is:

1. A signalling system for a number of stations on a common communication channel comprising a common signaling frequency, means to call all of the stations from any single station by said common frequency,

means to select any one of the called stations and transmit a message by said common frequency, and further means also operated by said common frequency at all of said stations for prohibiting the non-selected stations from effecting communication as long as trafiic with said selected station continues.

2. A signalling system for a number of stations on a common communication channel comprising means to call all of the stations from any single station on a common frequency, means responsive to said frequency at all of said stations operated periodically as long as reception of said fre uency continues, a selecting arrangement or each of said stations for sending a continuous selecting signal wave on said frequency, the selecting signal being of longer or shorter duration corresponding to the station with which communication is to be effected, and means whereby signalling communication is established by cooperation of said selecting signal with said second means.

3. A signalling systemfor a number of stations on a common communication channel comprising means to call all of the stations from any single station on a common frequency, mechanical means responsive to said frequency at all of said stations operated periodically as long as reception of said frequency continues; and means in connection with said first means at each of said stations for sending a continuous selecting signal wave on said common frequency of shorter or longer duration allotted to each of said stations respectively, said selecting signal cooperating with said mechanical means for establishing signalling connection between the calling station and the selected station.

4. A signalling system for a number of stations on a common communication channel, comprising a transmitting and receiving apparatus at all of said stations, means to call all of the stations from any single station on a common frequency, a mechanical element at all of said stations adapted to carry out periodical movements as long as reception of said frequency continues, cooperating means for prohibiting communication of said stations, means in connection with said first means at each of said stations for sending a continuous selecting signal wave on said frequency of a shorter or longer duration allotted to each of said stations respectively, and means for establishing signalling connectipn between calling station and selected station by cooperation of said selecting signal with said mechanical element.

5 A signalling system in accordance with clalm 4 according to which said mechanical element has the form of a lever provided with a contact movable relative thereto against the force of a spring, a further stationary contact also movable against the force of a spring and adapted to engage said first contact, whereby the relative position of said contacts is such that engagement takes place after a certain lapse of time corresponding to a dis tinct position of said lever in accordance with the respective duration of the selecting signal and means to disconnect said device and connect said apparatus to the signalling channel by the engagement of said contacts.

6. A signalling system in accordance with claim 4 in which said first means consists of a dial associated with a contacting device, means including a spring for setting said dial at a distinct position and releasing it to return to its zero position and means associated with said contacting device for sending out a selecting signal of distinct duration corresponding to the station which it is de sired to call.

7. The method of communication which consists in calling a number of stations by a train of oscillations of given frequency, selecting the desired station and then transmitting a desired signal on said frequency while at the same time keeping the remaining stations inactive by said same frequency.

8. The method of communication which consists in calling a number of stations on a train of oscillations of given frequency, selecting the desired station, transmittlng a. desired signal on said original frequency and simultaneously informing the remaining sta- 5 tions by means of such said same frequency that communication with the selected station is in progress.

In testimony whereof we aflix our sigma tures.

BRUNO ROSENBAUMQ OTTO POHLE. 

